1. Field of the Invention
The present invention relates to an optical transmitting device and an optical receiving device each having a receptacle type optical module.
2. Description of the Related Art
In a recent information communications field, massive amounts of information are required to be transmitted at high speed with an increase in amount of information, and the widespread use of high-speed high-capacity optical communication networks including an optical subscriber system is now proceeding. To achieve the widespread use of an optical subscriber system, a reduction in cost of an optical module is indispensable. The cost of the optical module includes a members cost, assembly cost, test cost, and adjustment cost. In particular, the assembly cost and the adjustment cost occupy a large proportion of the total cost. As means for reducing the assembly cost, a receptacle type optical module has been in the limelight in recent years.
Conventionally, among optical devices, a pigtail type optical module having such a structure that an optical fiber is attached to the end of an optical device is mainly used in general. However, in reducing the size and cost of the optical module, the presence of the pigtail fiber becomes a large bottleneck. For example, in the case of mounting the optical module in a communication device, a forming process for the optical fiber is necessary. Further, in carrying the optical module, merely storing the optical module into a carrying case requires a handling operation and a considerable number of man-hours. Further, in the case of automating the assembly of the optical module, the presence of the pigtail fiber becomes a bottleneck to full automation.
Further, in mounting an optical module on a printed wiring board in a soldering process as mounting surface-mount components or through-hole mount components, a so-called pigtail type optical module having an optical fiber cord is not suitable. That is, the optical fiber cord usually has a nylon coating, which has low heat resistance as melting at about 80xc2x0 C. in the soldering process. Further, the optical fiber cord itself causes a problem on accommodation and handling at a manufacture site, thus remarkably reducing an efficiency of mounting of the optical module on the printed wiring board.
Accordingly, to allow the soldering process for the optical module and reduce a manufacturing cost, the provision of a so-called receptacle type optical module having no optical fiber cord is indispensable. The receptacle type optical module has a connector portion adapted to detachably connect an optical fiber cord with a coating weak to heat. Since the receptacle type optical module has no optical fiber cord, high-temperature reflow soldering can be applied, so that the optical module can be mounted on a printed wiring board simultaneously with the mounting of surface-mount electronic components.
U.S. Pat. No. 5,875,047 discloses an optical transceiver unit. This conventional optical transceiver unit is assembled in the following manner. First, a printed wiring board is manually fitted to a lower case. Optical components are next manually mounted on the printed wiring board, and stop rings are manually mounted on the optical components to fix them. Finally, an upper case is manually fitted to the lower case, thus completing the assembly of the optical transceiver unit. In this optical transceiver unit disclosed in U.S. Pat. No. 5,875,047, the assembly is dependent on manual operations, causing a reduction in assembly workability, it is therefore desired to improve the assembly workability. Moreover, ground enhancement to the upper case is required for further improvement of the immunity to electromagnetic interference.
It is therefore an object of the present invention to provide an optical receiving device improved in the immunity to electromagnetic interference.
It is another object of the present invention to provide an optical transmitting device and an optical receiving device improved in the assembly workability.
In accordance with an aspect of the present invention, there is provided an optical device comprising a lead frame having a plurality of leads; a printed wiring board mounted on said lead frame and having a ground pattern; a ferrule assembly including a metal member, optical fiber holding means fixed to said metal member and having a through hole, and an optical fiber inserted and fixed in said through hole of said optical fiber holding means, said metal member being fixed to said lead frame; a semiconductor optical element fixedly mounted on an end face of said optical fiber held by said optical fiber holding means; an electrical circuit mounted on said printed wiring board; a wire for connecting said semiconductor optical element and said electrical circuit; an internal shield fixedly mounted on said ground pattern of said printed wiring board for covering said electrical circuit and said wire; and a resin mold package for enclosing all of said lead frame, said printed wiring board, said electrical circuit, said semiconductor optical element, said wire, said internal shield, and said ferrule assembly except a part of each of said leads, a part of said optical fiber holding means, and a part of said metal member.
The electrical circuit and the wire are covered with the internal shield, thereby improving the immunity to electromagnetic interference in an area where a feeble signal is passed. Preferably, the internal shield is formed of metal, and has a cutout for allowing injection of a molding resin into the internal shield and at least one air vent. Accordingly, the molding resin can be efficiently injected into the internal shield.
Preferably, the metal member has a cylindrical portion, and the resin mold package seals the ferrule assembly at the cylindrical portion. With this structure, a resin burr generated in a molding process is prevented from sticking to the optical fiber holding means such as a ceramic capillary, thereby allowing a reduction in connection loss by an optical connector.
In accordance with another aspect of the present invention, there is provided an optical device comprising a lead frame having a plurality of leads; a printed wiring board mounted on said lead frame; a ferrule assembly including a metal member, optical fiber holding means fixed to said metal member and having a through hole, and an optical fiber inserted and fixed in said through hole of said optical fiber holding means, said metal member being fixed to said lead frame; a semiconductor optical element fixedly mounted on an end face of said optical fiber held by said optical fiber holding means; an electrical circuit mounted on said printed wiring board; a wire for connecting said semiconductor optical element and said electrical circuit; a resin mold package for enclosing all of said lead frame, said printed wiring board, said electrical circuit, said semiconductor optical element, said wire, and said ferrule assembly except a part of each of said leads, a part of said optical fiber holding means, and a part of said metal member; and an external shield mounted on said resin mold package so as to cover said resin mold package.
Preferably, the external shield is fixed by welding at a plurality of positions to the leads. Preferably, the metal member has a cylindrical portion, and the resin mold package seals the ferrule assembly at the cylindrical portion.
In accordance with a further aspect of the present invention, there is provided an optical device comprising a lead frame having a plurality of leads; a printed wiring board mounted on said lead frame; an optical element module including an optical element package having a semiconductor optical element, and a ferrule assembly having:a metal member, optical fiber holding means inserted and fixed in said metal member, and an optical fiber inserted and fixed in said optical fiber holding means, said metal member being fixed to said optical element package and fixedly mounted on said lead frame; an electrical circuit mounted on said printed wiring board; and a resin mold package for enclosing all of said lead frame, said printed wiring board, said electrical circuit, and said optical element module except a part of each of said leads, an end portion of said optical fiber holding means, and a part of said metal member.
The above and other objects, features and advantages of the present invention and the manner of realizing them will become more apparent, and the invention itself will best be understood from a study of the following description and appended claims with reference to the attached drawings showing some preferred embodiments of the invention.